1. Field of the Invention
The present invention relates to a 64-bit PCI-ISA edge connector (64PCI-ISA). More particularly, the present invention describes a 64PCI-ISA edge connector that can plug into a 32-bit PCI-ISA (32PCI-ISA) slot.
2. Description of the Prior Art
The increasing complexity of processors has necessitated a corresponding increase in bus complexity. Such progress can be noted by the various bus standards in use today, such as ISA, 32-bit PCI and, most recently, 64-bit PCI. These standards have their corresponding edge connectors and slots.
Please refer to FIG. 1. FIG. 1 depicts an industry standard 64PCI-ISA edge connector 10 and its associated slot 20. The slot 20 is part of a passive backplane, a device which has only connectors mounted on its surface with a minimal amount of associated circuitry. Backplanes are common in industrial applications as they permit the rapid replacement of entire motherboards, as well as peripheral expansion boards, the backplane itself having a very low likelihood of failure.
The edge connector 10 has two distinct bus lines: an ISA bus edge connector 12 and a 64-bit PCI bus edge connector 14. The 64-bit PCI edge connector 14 has a 32-bit PCI edge connector 16 and a 64-bit PCI edge connector extension 18. The 32-bit PCI edge connector 16 provides full 32-bit PCI bus connectivity. The 32-bit PCI edge connector 16 with the 64-bit PCI edge connector extension 18 together provide full 64-bit PCI bus connectivity. A gap 30 with a predetermined width separates the 32-bit PCI edge connector 16 from the 64-bit PCI edge connector extension 18. Please note that the number of contacts shown in the edge connector 10 are for illustrative purposes only. The actual number of contacts may differ. The full specification for the number of contacts, and their function, is publicly available, for example, from the PCI Special Interest Group, or the PCI Industrial Computer Manufacturers Group.
The slot 20 comprises two distinct bus slots set a predetermined distance apart from each other: an ISA bus slot 22 and a 64-bit PCI bus slot 24. The 64-bit PCI bus slot 24 has a small separator in it (not shown) that corresponds to the gap 30. Each of the slots 22, 24 are actually a little bit longer than the lengths of their corresponding edge connectors, as indicated by the dashed lines 32. This excess length is required for the structural integrity of the slots 22, 24, and is a source of trouble when attempting to plug the 64PCI-ISA edge connector 10 into a 32PCI-ISA slot.
Please refer to FIG. 2. FIG. 2 depicts the 64PCI-ISA edge connector 10 adjacent to a 32PCI-ISA slot 40. The 32PCI-ISA 40 slot comprises two bus slots: an ISA bus slot 42, and a 32-bit PCI bus slot 44. These bus slots are set a predetermined distance apart, a distance equal to that between the two slots of the 64PCI-ISA slot 20. Consequently, the ISA edge connector 12, and the 32-bit PCI edge connector 16, should be able to plug into their corresponding slots 42 and 44, respectively. However, the 32-bit PCI slot 44 is a little too long, as indicated by the dotted lines 34. The extra material required at the ends of the 32-bit PCI slot 44 exceeds the width of the gap 30, and comes into contact with the 64-bit PCI edge connector extension 18. This makes it impossible to plug the edge connector 10 into the slot 40.
The 64PCI-ISA bus is relatively new. Many older systems are not equipped with such slots. Consequently, a manufacturer of computer boards must either make two versions of the board (a 32PCI-ISA version and a 64PCI-ISA version), or suffer a loss of customer base. Making two version of the same board is expensive, inefficient and may be confusing for the customer. Losing potential customers is often simply unacceptable.